1. Field of the Invention
The present invention relates to a control system/method for determining the direction of rotation of a shaft, such as a transmission input shaft, being monitored by a non-directional rotational speed sensor. In particular, the present invention relates to a control utilizing a non-directional rotational speed sensor for determining the direction of rotation of a vehicular transmission input shaft drivingly connected to an internal combustion engine, such as a diesel engine, by a selectively engaged and disengaged friction clutch.
2. Description of the Prior Art
Automated mechanical vehicular transmission systems, including an automated mechanical transmission having an input shaft drivingly connected to an internal combustion engine by an automatically operated master friction clutch, are known in the prior art, as may be seen by reference to U.S. Pat. Nos. 4,081,065; 4,361,060 and 5,275,267, the disclosures of which are incorporated herein by reference.
Vehicular clutch control systems for partially engaging a vehicular master friction clutch to a touch point or slipping condition are known in the prior art, as may be seen by reference to U.S. Pat. Nos. 4,646,891 and 6,071,211, the disclosures of which are incorporated herein by reference.
For smooth and rapid engagement of the master clutch during vehicle launch, it is desirable to engage the clutch in a modulated manner to achieve a desired amount of torque transfer and/or slip (i.e., engine speed minus input shaft speed). If the speed of the input shaft is sensed by a non-directional speed sensor, a problem may occur if the vehicle is rolling backward (vehicle rollback on a hill) at start-from-stop. Such a misreading of true directional input shaft speed may lead to rough engagement, undue wear and/or damage to the vehicle drivetrain and/or a false determination of clutch lockup if the rotational velocity of the input shaft happens to be equal but opposite that of the engine.
In accordance with the present invention, the drawbacks of the prior art are minimized by the provision of a control system/method which will allow a determination of forward or backward direction of rotation of a vehicular transmission input shaft utilizing a non-directional input shaft speed sensor.
The foregoing is accomplished by providing a control which, at start-from-stop conditions, will partially apply the vehicle clutch and determine if the sensed input shaft accelerates or decelerates. If the non-directional input shaft speed decreases, (i.e., if the input shaft decelerates), this is an indication that the input shaft is rotating in the opposite direction than the engine (it is understood that internal combustion engines, when driving, are unidirectional devices and have an idle speed exceeding expected initial input shaft speed). Based upon this determination of correct magnitude and direction of rotational speed, an appropriate engagement sequence may be instituted.
Accordingly, it is an object of the present invention to provide a new and improved control method/system for engaging a master friction clutch in a vehicular automated mechanical transmission system.
This and other objects and advantages of the present invention will become apparent from a reading of the following description of the preferred embodiment taken in connection with the attached drawings.